It doesn't matter what choice you make. The ending is basically exactly the same no matter what you choose to do. You're led to believe that throught the many many hours that you invest into the game, that what you choose to do matters in the ME universe, where in reality it actually means fuck all. Major choices throught the series end up having little or no impact whatsoever. The Rachni queen, the human reaper, who you shack up with, who you kill. None of it matters in the end, not a thing.
I'll be honest, ME3 starts brilliantly, but fades really quick and it fades well before the clusterfuck ending for me. When characters that you've met in 1 and 2 are basically thrown away by the writing team as footnotes, or given missions that are pretty much just a token tack on (like Samara, Jack, Jacob to name but 3) it's all just a fucking cop out. There's so many stupid plot holes that could have been solved easily. For example. Grunt. Tank born krogan who's more perfect than any other krogan. Instead of giving him a pissy little 2 min cameo in cut scenes on a moon where nothing happens about the rachni, why isn't it that it's Grunts dna that's needed with eve to cure the genophage? That would make complete sense. Instead he's given some shitty little battle, falls off a ledge only to be alright and then we don't see him again. The only bit that actually really made me go "fuck yeah, that's awesome" was the thresher maw and reaper fight. Most of the rest of it was toss in 3.
The whole game was so much more of a time sink rather than doing anything useful. The scanning was even worse in this one than in 2 (oddly I quite liked the lazy scanning in 2), the armour was shit if you tried to make it out of pieces, the specter weapons were shit because of the very poor selection.
But all that could have been forgiven if the ending had been handled properly. I agree with james it felt like it had been very rushed. not just the ending, but the whole thing. The writing was really poor, and the shit about the catalyst being a small star child smacked of desperation to be a bit out there, almost like the architect in the matrix. It was pointless and didn't need to be in there. Make the crucible be the ultimate weapon, make shepherd talk to harbinger, the ultimate reaper who you never see or hear very much about only at the end of about 3 sentances. Give us a choice to make a deal with the reapers or wipe them out. Not wipe out all synthetic life, that's fucking shit.
The options they gave us were shit, because the ending itself was shit. Then there's the bit about why is the normandy fleeing the battle and leaving you to die, as they'd have to have used the mass relay before you made your choice. Even that i could probably live with if it just had something at the end. Not just "oh look, it's some of your crew on a world" nice one.
I've invested at least 150 hours into this game, more as i'd played through 2 twice before playing 3. This isn't like a movie where i've sat for 2 hours and gone "that's a bit shit that ending" and headed off to do something else. I've invest a lot of hours into a game series and a universe that had engaged me on a level that films and serieses can never ever hope to replicate. That's why I, and so many others are fucking fuming at the cop out shitness of that ending. I can't speak for others, but I want to see what happens to my crew, i want to see what Tali (who i'd been with for the series) had gone on to do, I want to see what my choice meant for the galaxy.
Ultimately I want closure as the game feels like it never finished. I'll shut up now as i'm probably not putting it down right